QB Issue Resolution:

bring up a balance sheet
double click on inventory asset
click customize
change total by to item detail
set the report date range to ALL
refresh the report

scroll down, if there is a section called No item, those transactions are your problem

Resolution for Issue 'Why would Inventory Valuation Summary and Balance Sheet Details be different?' available: Yes (Solved).
Source: Intuit Community forum.

Why would Inventory Valuation Summary and Balance Sheet Details be different?: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

Support for Balance Sheet
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Error Recovery for Balance Sheet [Canada]
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